The World Organization for Animal Health (Office International des Epizooties—OIE) maintains a list of economically important pathogenic organisms responsible for significant damage and devastation to commercial food aquaculture industries, including shellfish, throughout the world. The United States Department of Agriculture (USDA) at both the national and the state level requires periodic mandatory reporting of any confirmed cases of these pathogens within the United States as part of a global cooperative effort to limit the movement of pathogens to previously uninfected areas. For example, the pathogenic protozoa Perkinsus marinus (P. marinus) and Perkinsus olseni (P. olseni) are both OIE “reportable” or “notifiable,” but the reporting system is intended to prevent their introduction into the Indo-Pacific and North America, respectively. Perkinsus species (Perkinsozoa, Alveolata) are the causative agents of perkinsosis in a variety of mollusk species. Perkinsus species infections cause widespread mortality in both natural and farm-raised oyster populations, resulting in severe economic loss for the shellfish industry and detrimental effects on the environment. In particular, P. marinus causes significant mortalities in the economically important Eastern oyster, crassostrea virginica, along the east coast of the United States and the Gulf of Mexico. Perkinsus olseni has a broad geographic range extending from the Pacific Ocean around Japan and Eastern Asia to Australia and New Zealand, areas of the European Atlantic and the Mediterranean. The western hemisphere had remained free of P. olseni, with the exception of one report in Uruguay until it was discovered in ornamental reef clams, Tridacna crocea, legally imported into Florida, USA by the aquatic ornamental trade. The ornamental industry is under increasing scrutiny as the source of introduced exotic pathogens as it is not regulated by the USDA and is not required to test, quarantine, or provide health certificates.
There is growing concern among domestic and international trade partners that the USA is experiencing uncontrolled introduction of serious exotic pathogens through global trade from distant ecosystems in addition to ongoing issues with domestic pathogens impacting aquaculture production and human health. Current testing methods are not performed at the sampling location and require significant delay, expense, and expertise. Owners of saltwater aquaria containing P. olseni-infected ornamental clams and water in the USA have no way to test their effluents prior to discharging them into a drainage system or the environment.
Current testing methods for aquatic pathogens require transport of sampling material to a testing location. The commonly used methods require several days and include growing the organism in specialized media, detection with specialized molecules, or purification of genetic material followed by molecular testing. Currently, the standard diagnostic method for Perkinsus species infections has been the Fluid Thioglycollate Medium (FTM) assay detection. However, it takes several days to do the detection using this method. The polymerase chain reaction (PCR)-based technique is also used to diagnose Perkinsus, but it is quite expensive and time-consuming, and requires exquisite controls to assure specificity and accuracy. Clearly, such methods are slow and impractical to be used in the field. Furthermore, these methods require a dedicated testing location and staff and significant specialized training. In addition, they require a variety of expensive instrumentation and reagents, and involve multiple steps with potential failure at many stages. Replication in duplicate or triplicate is often necessary, which increases the time and costs.
Thus, there exists a need in the art for improved monitoring and regulation of aquatic pathogens for the aquatic industries, research, and home use.